There is a known misacceleration mitigation device which mitigates acceleration or start of a vehicle by suppressing an engine output even when an accelerator pedal is pressed in, if an obstacle is detected within a predetermined distance in front of the vehicle by an obstacle detector while the vehicle is moving at a predetermined speed or less or while the vehicle is standing.
For instance, Patent Document 1 (JP2014-29591A) discloses an erroneous start suppression device for a vehicle, which includes a travel-path prediction unit for predicting a travel path of a vehicle on the basis of a steering angle. An obstacle detected by a detector is regarded as an obstacle for an erroneous start suppression control only when the detected obstacle is in the predicted travel path, and an obstacle detected by the detector is not regarded as an obstacle for the erroneous start suppression control when the detected obstacle is off the predicted travel path.
In the erroneous start suppression device disclosed in Patent Document 1 (JP2014-29591A), three infrared beams (left, center, and right) are emitted in front of the vehicle to detect an obstacle in front.
An obstacle detection device emits the three infrared beam waves simultaneously in front of the vehicle, and the first infrared beam wave is emitted slightly to the left side in front of the vehicle so as to form the first detection region S1 that has a fan shape in a planar view and expands in a horizontal direction in front of the vehicle at a predetermined expansion angle. The second infrared beam wave is emitted to the front of the vehicle so as to form the second detection region S2 that has a fan shape in a planar view and expands in a horizontal direction in front of the vehicle 1 at a predetermined expansion angle. The third infrared beam wave is emitted slightly to the right side in front of the vehicle so as to form the third detection region S3 that has a fan shape in a planar view and expands in a horizontal direction in front of the vehicle at a predetermined expansion angle. The above first to third detection regions S1 to S3 are arranged next to one another in a horizontal direction, and collectively form a single integrated detection region S of a wide angle in front of the vehicle 1.
However, the three infrared beams (left, center, and right) in Patent Document 1 (JP2014-29591A) forming the first to third detection regions S1 to S3 have similar expansion angles and obstacle-detection distances in the horizontal direction. Thus, if an effective distance for detecting an obstacle is extended, the infrared beams at both of the left and right sides would be emitted beyond the width of the vehicle to detect a pedestrian or an object in a side-strip region, and thereby the obstacle detection in front of the vehicle includes an erroneous judgment, which presumably causes a problem in detection accuracy.
Thus, there is a technique under consideration which prevents unnecessary suppression of engine torque and improves the accuracy of the misacceleration mitigation control by imposing a limitation on the obstacle-detection distances of the infrared beams at the left and right sides so that the infrared beams do not reach beyond the width of the vehicle to prevent erroneous judgments, i.e., by performing the control only when an obstacle is detected within the range of the width of the vehicle.
However, if a limitation is imposed on the obstacle-detection distances of the left and right infrared beams to make the center infrared beam long, there may be a case in which the center infrared beam detects an obstacle first and suppresses the engine torque, but then, as the vehicle moves forward, the obstacle hides beneath the effective range of the center infrared beam or deviates to the left or right before entering the effective range of the left or right infrared beam, thereby becoming undetectable. In this case, the suppression once imposed on the engine torque would be canceled, and presumably, the risk of collision with the obstacle would increase.